The present invention is directed to a borehole drilling assembly and in particular to an assembly for drilling and completing deviated boreholes.
Deviated boreholes are drilled using whipstock assemblies. A whipstock is a device which can be secured in the casing of a well and which has a tapered, sloping upper surface that acts to guide well bore tools along the tapered surface and in a selected direction away from the straight course of the well bore.
To facilitate the use of a whipstock, a section of casing is used which has premilled window openings through which deviated well bores can be drilled. The whipstock can be positioned relative to the window using a landing system which comprises a plurality of stacked spacers mounted on a fixed mounting device at the bottom of the casing and defining at the top thereof a whipstock retaining receptacle, or by use of a latch between the whipstock and the casing. A stacked landing system can cause difficulty in aligning the whipstock with the window opening as the distance between the mounting device and the window increases. The whipstock may also turn during the drilling or setting processes resulting in the deviated well bore being directed incorrectly and/or the well bore tools being stuck in the wellbore. Sometimes a latch system is used to overcome some of these disadvantages. However, the latch can sometimes disengage between the whipstock and the casing, allowing the whipstock to turn or move down in the casing. After the deviated wellbore is drilled, it can be left uncompleted or completed in any suitable way. To seal the deviated wellbore hydraulically from the main casing, a liner can be installed and cement can be pumped behind the liner. This is expensive and often creates obstructions in the main casing which complicates removal and run of the tools. When the tools are used in horizontal primary bores, new problems arise. Running and retrieval tools which are useful for vertical tool manipulation are not always useful in horizontal applications.
An assembly for drilling and/or completing a deviated wellbore has been invented. In one aspect the assembly includes a toolguide which can be positioned relative to a window opening in a casing section and releasably locked in position. The toolguide or portions thereof can have applied thereto a coating which prevents damage to the metal components of the toolguide and facilitates removal of the toolguide from the wellbore after use.
A tool guide for creating deviated borehole branches from a wellbore includes a whipstock including a sloping face portion and a lower orienting section, including at least one latch biased radially outwardly from the orienting section and positioned in a known orientation relative to the sloping face portion and a latch locking means to releasably lock the latch in an extended position, the latch locking means being actuated to lock the latch by torsion of the mandrel within the lower orienting section.
Each latch of the orienting section is selected to fit within and lock into its own latch receiving slot formed in the casing. When the latch of the orienting section is locked into the latch receiving slot the toolguide will be maintained in position in the casing. Preferably, the casing includes at least one premilled window opening positioned in known relation relative to the latch receiving slot. Preferably, a removable liner can be positioned in the casing to close the window opening temporarily and to cover the latch receiving slot.
The orienting section can be releasably connected to the whipstock. Such connection is preferably by connectors such as, for example, shear pins to the whipstock so that these parts can be installed together into the casing. Preferably, the connectors are selected such that the sections can be separated by an application of force sufficient to overcome the strength of the connectors. This permits the whipstock and the lower section to be separated and removed separately should one part become stuck in the casing.
The sections are movable relative to one another and means are provided to translate such movement to actuate such means as a seal.
Preferably, the lower orienting section includes a mandrel engaged slidably and rotatably within an outer housing. The mandrel is releasably connected to the whipstock and moveable with the whipstock. Preferably, the latch locking means is an extension of the mandrel. The extension can be formed to fit behind the latch to lock it in the outwardly biased position.
Another toolguide for creating borehole branches from a wellbore, the toolguide having a longitudinal axis and comprising a whipstock including a sloping face portion, a lower orienting section, the whipstock and the lower orienting section being connected and moveable relative to each other along the longitudinal axis of the toolguide, and an annular sealing means mounted below the whipstock, the annular sealing means being actuatable to expand and retract upon movement of the whipstock and the lower orienting section relative to one another.
The whipstock is attached to a central mandrel of the lower orienting section. The central mandrel is engaged slidably and rotatably within an outer housing of the lower orienting section. The outer housing carries the annular sealing means which is actuatable to expand or retract by movement of the mandrel within the outer housing. Preferably, the outer housing includes a first section and a second section and disposed therebetween the annular sealing means. The first section is moveable toward the second section to compress the annular sealing means therebetween and cause it to expand outwardly. In this embodiment, preferably the mandrel has a shoulder positioned thereon to abut against the first section and limit the movement of the mandrel into the outer housing. Abutment of the shoulder against the first section causes the first section of the housing to be driven it towards the second section and the annular sealing means to be compressed and expanded outwardly.
Previous orienting tools were difficult to use because it was necessary to run the tool to a known depth and then search around for the position of the slot for accepting the latch on the tool. Because the latches of some orienting tools have to be biased outwardly on the trip down into the well, it has been difficult to use the orienting tools in wells, for example, having more than one lateral window and therefore more than one orienting slot for accepting the latch of the tool. To the problem of having the latch lock into the incorrect slot, where multiple slots are present, it has been necessary to shape the slots in the casing such that they will only accept one form of latch. This solution presents logistical problems, however, and limits the number of slots which can reasonably be positioned in the casing.
Thus, in accordance with one broad aspect of the present invention, there is provided an orienting tool for positioning in a well bore casing having a profile positioned therealong, the tool comprising: a body; at least one member mounted on the tool body and biased outwardly, at a selected pressure, therefrom, the selected pressure being great enough to permit determination of when the at least one member has moved past the profile but not being so great as to prevent the at least one member from moving past the profile using normal force.
The at least one member can be a spring loaded dog or an arm such as, for example, a part of a collet, a collar locator or any other means. In preferred embodiment, the at least one member is part of a ring of dogs mounted about a circumference of the tool body and biased outwardly therefrom. The at least one member preferably operates to position the tool at a selected pressure of 20,000 to 30,000 psi. At this pressure, when the member passes a profile, there will be a indicative overpull or decrease in drill string weight.
The at least one member can be biased outwardly by any desired means such as, for example, springs. In a preferred embodiment, the biasing means is selected to exert increased pressure as the depth of the tool is increased. This biasing means is preferred as it provides that less force is required to move the tool through the casing at shallower depths but requires greater force to be moved through the casing when it is at greater depths and, therefore, when there is greater available drill string weight to act on the tool. One such biasing means is sensitive to hydrostatic pressure and applies a pressure to the at least one member which increases with an increase in hydrostatic pressure of the fluids about the tool. It may be necessary to set an upper limit for the selected pressure applied to the at least one member.
The profile and the at least one member are preferably correspondingly positioned so that the at least one member will be affected by the profile regardless of the rotational orientation of the tool within the casing. To avoid forming a protrusion which extends inwardly from the casing inner surface and reduces the ID of the casing, preferably the profile is a groove sized to accept the at least one member therein. In a preferred embodiment, the groove is a radial groove extending about the ID of the casing.
There can be more than one profile along a length of casing. Where more than one profile is present along the casing, the at least one member will be affected by each profile in a similar manner. Preferably, the profiles are non-selective. The specific profile which is affecting the member can be determined using tool depth information, the measurement of which is well known in the art.
Where it is desired, in addition to positioning the tool at a selected orientation along the casing, to position the tool at a selected rotational orientation within the well, the tool can further comprise a latch for fitting into a slot positioned at a selected rotational position about the center axis of the casing. The tool is selected to provide for rotation of at least the portion of the tool carrying the latch to permit the latch to be located in its slot. In one embodiment, the tool body includes a first part carrying the at least one member, a second part carrying the latch and a joint positioned therebetween for permitting the second part to rotate relative to the first part and preferably also to move out of axial alignment with the first part.
The orienting sections according to the present invention can be used to orient whipstocks as well as other tools such as, for example, retrieval tools, sleeve shifting tools and lateral completion tools.
A whipstock for use in creating wellbore branches from a well bore can have a main body formed of a first material of reduced diameter to facilitate washover or engagement by die collars or overshots. The main body has extending out therefrom centralizers such as stand off rings or extensions the main body. Sometimes a coating material is disposed at least over a portion of the main body, the coating material being softer than the first material and being resistant to oil and gas.
In a whipstock having a main body of reduced diameter relative to centralizers formed thereon, it has been found that the width of the sloping face portion is greatly reduced. This reduces the surface area which is available to guide the drill bit or mill off the whipstock face and the mill or drill bit tends to roll off the sloping face portion in the direction of rotation of the drill.
To prevent roll off and to centralize and stabilize the upper tapered end of the whipstock, while continuing to facilitate washover procedures, a whipstock is provided including a main body having an outer surface, a sloping face portion formed on the main body and having a slope angle and an extension formed on the main body about the sloping face such that the diameter of the extension is greater than the diameter of the main body.
Preferably, the extension about the sloping face portion forms an effective diameter which is substantially equal to the drift diameter of the casing into which it is to be used. The extension preferably conforms to the slope angle of the sloping face portion and, where the sloping face portion has a curvature, follows and continues the curvature of the sloping face portion.
The whipstock can include centralizers extending out from the main body. Preferably, the effective diameter of the whipstock at the centralizers is substantially equal to the effective diameter of the whipstock at the extensions.
In one embodiment, the main body has applied thereto a coating, for example of polymeric material. The coating material can be applied against the extension and the centralizers, if any.
Running and retrieving tools are required for moving the tools through the well bore. Previous running tools for whipstocks used shear bolts for attachment between the running tool and the whipstock. These shear bolts are prone to shearing prematurely if the whipstock is bumped at surface while entering the will or sue to running the assembly through a tight area in the casing. The shear bolt may also shear prematurely if the assembly is rotated.
A new tool has been invented which is positively latchable to the whipstock in a manner that allows forces to be applied upwardly or downwardly as well as rotationally without risk of prematurely releasing the whipstock. At the desired time of release, hydraulic pressure is applied to the tool to unlatch it from the whipstock.
In accordance with a broad aspect of the invention, therefore, there is provided a running/retrieval tool for moving a well tool through a well bore casing, the running/retrieval tool comprising: a body; a latch for releasably engaging the well tool and being driven to move between a retracted position recessed in the body and an extended position in which a portion of the latch extends from the body; and a guide selected to act against the well tool to guide the latch into engagement with the well tool.
The latch can be driven between the retracted position and the extended position by any desired means. Preferably, the drive means for the latch can be controlled from surface and can be, for example, a hydraulic system.
The guide is formed on the tool and can be selected to engage with the well tool in such a way as to transmit rotational energy to the well tool. A key can be provided on the tool to assist in the location of the tool relative to a well tool to be retrieved. In a preferred embodiment, an outwardly biased key is provided which is engage able into an orienting slot formed on the casing section adjacent the mounting position of the well tool to be used with the running retrieval tool.
In another embodiment, the running/retrieval tool according to the present invention includes a outwardly extendable and retractable key useful for applying force against the casing in which the tool is positioned to urge it toward one side of the casing. The key can be extendable by a hydraulic system.
A casing section for a deviated wellbore junction comprises a cylindrical casing tube having a central axis and a window opening formed therein. A sleeve having an opening therein is mounted relative to the casing tube to move between a first position in which the opening of the sleeve is aligned with the window opening of the casing tube and a second position in which the opening of the sleeve is not aligned with the window opening of the casing tube.
Another casing section for a deviated wellbore junction includes a casing tube having a central axis and a window opening formed therein. A sleeve having a first opening and a second opening therein is mounted relative to the casing tube to move between a first position in which the first opening of the sleeve is aligned with the window opening of the casing tube and a second position in which the second opening of the sleeve is aligned with the window opening of the casing tube.
Preferably, sealing means are disposed between the casing tube and the sleeve. These sealing means are preferably selected to effect a hydraulic seal between the parts. In one embodiment, the sealing means are formed of deformable materials such as rubber or plastic and is disposed around the opening of the sleeve and along the top and bottom thereof.
In a preferred embodiment, the sleeve has formed therethrough two openings. The first opening is sized to allow access to the window opening of the casing section by deviated borehole tools and the second opening is smaller than the first opening.
In one embodiment, the sleeve is disposed within the casing tube in a counterbore formed therein such that the inner diameter of the sleeve is greater than or substantially equal to the inner diameter of the casing away from the position of the sleeve.
Preferably, the window of the casing is formed to accept a flange of a junction fitting such as, for example, a tieback hanger of a branched wellbore. In a preferred embodiment, the sleeve is selected to seal against the flange of the fitting.